AS: Most of the game was done before I knew Robin was going to come and work on it; I just hadn't figured out how I was going to do all the sounds. Initially, it was a prototype. I liked the verisimilitude of viewing your progress through some kind of radar, so that everything in the world is going to be fed back to you through this one interface, this one believable piece of technology. It's going to have your fuel, your air, your speed, your direction and the types of things you can run into. It was about a single idea that I wanted to test.

In Canabalt the buildings are generated based on the speed that you're running, and each building is generated one at a time. So however fast you're running now is the input that is used to work out what is an interesting obstacle for you to encounter next. It always makes sure that jumps are achievable, but have an interesting level of difficulty.

For me, that's interesting because it allows you to hit a box and slow down, and it doesn't ruin the whole game, because it instantly reacts to the change in your speed.

There was a principle under there that I thought was really interesting: this is a cool thing you can do with a procedurally generated game that's not just to avoid doing level design.

If everything's procedural, it can be reactive. You can have a game environment that responds to the choices that players make. Dynamic difficulty adjustment is sort of an expression of that in big triple-A games, but it's the most boring version. The Left 4 Dead director AI is a pretty good example.

A lot of Capsule's procedurally generated world is actually really Left 4 Dead-inspired. It's actually monitoring how you're doing and trying to create scenarios that are emotionally potent. If you have lots of oxygen and health it's going to start inventing more challenging things for you. As your oxygen and fuel dwindle, it's going to be much more likely that you'll just barely stumble across some small form of sustenance. All that stuff is actually programmed in, which in one way is a horrible lie, but in another way, how else would you do this except by having a scripted level with set distances, which couldn't be replayed?

It's like telling any story that involves a last-minute save.

AS: Yes.

And also, the player might miss that bit of oxygen.

AS: Yeah, and especially if your power's low and you're afraid of pulsing [which reveals objects], because that uses up power. So it doesn't always save the day, but it increases the likelihood that there will be a really exciting scenario. There is a lot of programming in that. To me, it seems to work, and systemically that's one of the core things that Capsule is supposed to do. [The] world generation stuff is more complex than Canabalt but still not as complex as it would have to be to happen in a Resident Evil game.

Why did you decide to give the player an objective, rather than letting them just explore?

AS: Part of it was to give a purpose to the cool looking compass things at the bottom. Part of it was to feed more atmosphere back in. In the festival version, the story gets into the nitty-gritty really fast and it doesn't explain very much.

When you play it at home it's a lot more of a slow-burn type of thing where at first you know nothing -- there's no narrative you listen to on the way to the game [as there is in the festival version] -- you just start it up, and the first part of the game is you figuring out what is going on with the controls and the gameplay, but also with the story. So when we compressed it for the festival we took a lot of that out and rearranged the story.

The only way people can play the game at home is if they subscribe to Venus Patrol. Did you know this when you were making the game?

AS: Originally, I thought people were only going to be able to get it by participating in the Venus Patrol Kickstarter. It was fine because the game didn't take that much work, and I'd already done most of the systemic prototyping.

But did it affect how you made it? That it was only for this small audience?

AS: I was way more willing to make it weirder. We could have made it so that you would use oxygen at a similar rate that you burn fuel, as opposed to being slower like it is now, to ensure that if you ran out of juice you would die of oxygen loss almost immediately afterwards. [But I was thinking] this is going to this weird, picky audience. It won't freak them out if we do things differently than some other games do. You don't consume air particularly quickly and everything is set up to make it much more likely that you'll just run out of fuel and just be stuck there, and just have to deal with it. No games make you do that. It's such a horrible thing to do to a player.

Super Meat Boy: you make a mistake, it's fine, go back to the beginning of the level and try it again. In Capsule it's less about punishment, it's more part of the cycle. Part of the fun -- if Capsule's fun -- is, "Oh God, what happened? I don't want to listen to myself asphyxiate. This is making me uncomfortable." That's the "pleasure" of it.